iCloud does not backup your Safari Bookmarks in the same way that it backs-up your phone.
Bookmarks, Contacts, Calendar, Reminders and Notes are pushed to your account, and if you have multiple devices logged in with the same account, that information is then pushed to those devices.
If you delete an entry from one device, it is then deleted from the other devices as well simultaneously.
iCloud backs up your phone's Data (from apps), Settings and the contents of your Camera Roll.
iCloud backs up once every 24 hours automatically if your device is on WiFi, plugged into a power source and not in use. Example:
If you plug in your phone to charge at 1pm and you let it sit their, your phone will then back-up around 1:10pm. Now lets say that the next day you are out running errands and don't get home until 3pm. Your phone will not begin to backup until you plug in your iPhone to charge again.